It is frequently desirable to monitor an inventory to reduce pilferage. One means for doing so is by measuring the change, as a function of time, of the weight of a support structure on which the inventory is stored. The change in weight is monitored by one or more scales on which the support structure rests. U.S. Publication No. 2005/0077352A1 teaches one example of an inventory monitoring system which uses weight changes to monitor inventory. To avoid erroneous readings due to artifacts resulting from loading and unloading inventory from the support structure, it is desirable to configure the support system to limit the motion of the supporting structure to essentially vertical motion, and to rapidly damp any transitory motion associated with horizontal motion. This is particularly true for an inventory of items in a retail setting, where the frequent loading or removal of items causes torques on the supporting element due to friction, impacts, and changes in the distribution of weight.
U.S. Pat. No. 4,481,985 teaches an apparatus for measuring fluent material where stabilizers are interposed between a conical cylindrical chamber and a frame. The stabilizers are a pair of leaves that are connected between the frame and limbs attaching to each side of the chamber and serve to inhibit any nutation, tilt or other disorientation of the chamber from its optimal vertical position due to tangential introduction of the fluent material. This apparatus would not be suitable for storing and monitoring an inventory of individual product items, and the stabilizers do not appear to be designed to counter forces applied at a large vertical distance from the stabilizers.
U.S. Pat. No. 4,261,428 teaches a platform weighing apparatus for measurement of a load with a load cell. The apparatus has a load supporting platform which is linked to a stationary base platform by a stabilizing system having two pairs of arms. Each pair of arms is pivotably attached at one end to the load support platform, and at the other end to the base platform, with the arms in each pair rigidly connected so as to pivot together. The pivot axes of the pairs of arms are arranged perpendicularly. This apparatus is reported to be designed to monitor heavy loads, and thus the massive structure of the connection, the rigid connections between the arms to resist torsional loads, and frictional resistance to pivoting may not affect its performance in this role; however, this apparatus would not be well suited to measuring small weight changes associated with shelved inventory.
Thus, there is a need for a shelving system which can be used with a load cell to allow monitoring an inventory of retail items as the items are loaded onto and removed from the shelving system.